1. Field of the Invention
The present invention relates to signal processing circuits, and particularly to a current-mode CMOS logarithmic function circuit that produces an output current proportional to the logarithm of the input current.
2. Description of the Related Art
Nowadays, a significant increase in the use of CMOS technology for realization of analog circuits has been observed. Current-mode circuits have received more attention than their voltage-mode counterparts. CMOS circuits with nonlinear functions will greatly enhance signal processing capabilities, such as clock recovery, waveform generation, adaptive filtering etc. Logarithmic function circuits produce an output that is proportional to the logarithm of the input. These types of circuits are used in applications that require compression of analog input data, linearization of transducers that have exponential outputs, and analog multiplication and division. Logarithmic functions are also widely used in many signal processing applications.
However, conventional logarithmic function circuits suffer from a number of limitations, including the absence of low voltage operation capacity, limited dynamic range, etc. Thus, a current-mode CMOS logarithmic function circuit solving the aforementioned problems is desired.